The invention relates to a solenoid valve with an inlet connection and an outlet connection, having between them a blocking device with a valve seat, a closure member and an armature, which influences a position of the closure member in relation to the valve seat.
A solenoid valve of this kind is known from, for example, DE 34 30 724 A1. When a coil is supplied with current, a magnetic field is generated, and the armature moves. The closure member, which is arranged on the armature, is lifted from the valve seat by this movement. When the magnetic field disappears, the armature is moved back under the force of a spring, so that the closure member comes to rest against the valve seat again. For this purpose, the closure member has a predetermined embodiment, which is in certain ways resilient, so that a damping is obtained, when the closure member strikes the valve seat.
DE 44 04 740 A1 describes another solenoid valve with an armature, which is displaceable against an end stop. Between the armature and the end stop damping means in the shape of a compressible ring are arranged.
DE 197 39 007 A1 shows a solenoid valve with a hydraulic damping, the hydraulic damping being arranged in an iron core and having a tappet extending from the iron core, a damping piston being arranged on the tappet.
In all cases, the damping of the movement of the armature requires additional parts and component groups, which make the embodiment of the valve complicated.
The general object of the present invention is to minimise wear.
In a solenoid valve as mentioned in the introduction, this task is solved in that the armature is arranged in a housing, dividing it into two chambers, and that the armature has a movement stroke with several sections, one first section being in the form of an idle stroke, during which a connection between the two chambers is open and the position of the closure member in relation to the valve seat does not change, and a second section being in the form of an effective stroke, during which the connection between the two chambers is closed and the armature causes or permits a movement of the closure member.
Thus, a certain damping is obtained through the movement of the armature. In a solenoid valve, which is suited for controlling a fluid, for example, a solenoid valve for a humidification system, certain leakages always exist, which cause the housing to be filled with fluid. When the armature moves, it displaces the fluid from one chamber of the housing into the other chamber. This is possible, because the connection between the two chambers is open during the idle stroke. At the end of the idle stroke, that is, at the beginning of the effective stroke, however, the connection is closed. In one of the chambers, fluid reserves have then been created, which are basically not compressible. An additional movement of the armature is thus only possible to the extent, to which leakages exist. Thus, the term xe2x80x9cclosedxe2x80x9d does not indicate a hermetically sealed closing. On the contrary, within the range of the leakages mentioned, a certain fluid penetration is still possible. However, this fluid penetration is throttled in such a way that a movement of the armature during an effective stroke is only possible against a certain resistance. This resistance causes a damping of the movement of the armature, so that the armature reaches an end stop or acts upon the closure member only with a reduced speed. Through this damping, the wear is kept small. The armature can act directly upon the closure member. However, it can also act indirectly, for example in that the armature, or a part being connected with the armature, is lifted from the closure member, thus permitting a movement, which had until then been blocked.
Preferably, the closure member has a tappet, which acts upon a separate closure element, the effective stroke being larger than the maximum opening movement of the closure element and the pressure in one of the two chambers acting upon the end of the tappet turning away from the closure element. With this embodiment, it is achieved that due to the pressure in the chamber, the tappet always bears on the closure element. This means that the tappet can no longer strike the closure element abruptly, which could cause an increased wear or even a damage to the tip of the tappet or of the closure element. When the closure element is separated from the tappet, that is, both are made as independent parts, there is an increased freedom with regard to the selection of materials for both elements.
Preferably, a closing force device acts upon the closure element in the direction of the valve seat, and the armature acts against the closing force device. In the simplest case, the closing force device is made as a closing spring, which presses the closure element against the valve seat, if required; a tappet is inserted between them. The armature now reduces the force, with which the closure member is pressed against the valve seat. When the force gets smaller than force generated by the pressure of the fluid, which acts upon the closure member by way of the valve seat, the closure member is lifted from the valve seat and the valve opens. This means that the valve is closed when de-energized. In such a valve the closing movement appears through the force of the closing force device. However, this force can only act upon the closure element in a damped manner, as the closing requires a movement of the armature, which is damped by the fluid trapped in the chamber facing the closure element.
Preferably, the armature closes the connection. Thus, additional control elements are not required. The closing and the opening of the connections between the two chambers appear in the course of the movement of the armature at the correct instants.
It is particularly preferred that, the armature has a channel extending in the movement direction and having a narrow passage, which comes to rest on a movably supported sealing face at the end of the first section. The narrow passage, which has, for example, a circumferential shoulder, forms, together with the sealing face, the combination, which leads to a closing of the connection between the two chambers in the housing. Thus, the closing of the connection can be effected by a simple displacement of the armature.
Preferably, the sealing face acts upon the tappet. Thus, it is ensured that the effect on the tappet appears at the same time as the closing of the connection between the two chambers. This means that the armature is lifted from tappet at the time, when the connection is closed, or it strikes the tappet, when the connection is opened.
Preferably, it is ensured that, when the valve is open, the closure element closes an auxiliary valve seat, which is connected with a tank connection. This embodiment is particularly advantageous in connection with a humidification system, as this embodiment prevents orifices of the humidification system from dripping, when the valve is closed. When the valve is closed, the outlet connection is connected with the tank connection, to permit remaining fluid to flow off.
Preferably, the closure element is supported in a guiding device. The guiding device ensures that during a movement the closure element cannot be laterally displaced, but is always guided straight to the valve seat or to the auxiliary valve seat. Thus, the function of the valve is also guaranteed with a high degree of safety, even when the closure element and the tappet are made as two separate parts.
It is particularly preferred that the guiding device has an opening, in which the closure element is arranged, the diameter of the opening being equal to that of the closure element plus a predetermined play. There is nothing preventing a generous dimensioning of the play. At any rate, it must be so large that the closure element can move undisturbed in the opening of the guiding device. On the other hand, with this embodiment, the guiding device has an additional task, particularly when the valve is open and the closure element has to close the auxiliary valve seat. In this connection, the guiding device also serves the purpose of preventing, or at least hampering, a short-circuit between the valve seat and the auxiliary valve seat, during the whole movement of the closure element. Among other things, this is caused by the closure element practically filling the opening in the guiding device, so that a direct fluid flow between the valve seat and the auxiliary valve seat is only possible to a very limited extent.
It is preferred that the guiding device has a guiding member in the shape of a bowl opening in the direction of the valve seat. When, during its movement, the closure element closes the opening in the guiding device, the fluid flowing through the valve seat is led away by the auxiliary valve seat through the guiding member, that is, in a manner of speaking flows a little backward on the outside of the valve seat. As the time, during which the closure element moves from the valve seat to the auxiliary valve seat or vice versa, is relatively short, this diversion of the incoming fluid is sufficient to prevent the short-circuit.
Preferably, the valve has a nominal flow rate of 1 to 5 l/min. A nominal flow rate of this size is sufficient for humidification systems. With the valve described, this is easily controlled.